Those skilled in the art of evaluating the print quality of data carrying graphical symbols understand the need to generate a plurality of evenly spaced scan or imaging lines. Importantly, the plurality of imaging lines are preferably taken substantially orthogonally across the elements of a graphical symbol, and preferably with each at a different position along the height of the symbol. This is particularly important when there is a need to provide full and complete print quality verification to well known industry standards. For example, typically verifiers that provide a quality reporting that meets ANSI, AIM, ISO, and/or other existing industry quality standards, will often employ imaging sample data from at least 10 discrete imaging positions spaced along the height of the imaged data carrying graphical symbol.
A number of varied approaches have been utilized for generating a group of (preferably evenly) spaced and substantially parallel scan or imaging lines. A first well known approach mounts a line scanning device in position to scan data carrying graphical symbols as they are printed on a printing web. In this case the media upon which the data carrying graphical symbol is printed is moving past the scanning device, and inherently provides spaced parallel scans as the graphical symbol moves into and out of the field-of-view of the scanner unit. In similar fashion, the prior art teaches the technique of “raster laser scanning” wherein a linear scanner is employed in a stepped fashion, to produce a large plurality of very closely packed (and inherently evenly spaced) scan lines of a target indicia. In each of these approaches, the rate of motion between the scanning means and the indicia is known—making it relatively easy to produce and or select a plurality of suitably spaced scan or imaging lines.
Another more recent approach is to employ an imaging device to image the entire data carrying graphical symbol, and often a surrounding portion of the substrate upon which the graphical symbol is printed. Once the area containing the graphical symbol is imaged and stored, a post-processing can be applied to determine a plurality of ‘virtual imaging lines’, which may also be termed virtual scan lines. In this latter case, actual scanning is replaced by a software algorithm that selects a subset of imaging data samples, and processes them to provide an indication of the print quality of the imaged data carrying graphical symbol.
Each of the cited prior art approaches has another characteristic in common: the imaging or scanning device is fixed in a pre-selected location, or alternately movably mounted so that any motion of the imaging or scanning means is known, controlled, and relatively steady/predictable.
A truly low-cost method of capturing and collecting a plurality of evenly spaced imaging lines involves the manual use of a linear scanning or imaging means. For example, it is known in the art to employ a linear scanning means, such as a linear laser scanner or a linear imaging CCD device, and simply have the operator provide a sliding or sweeping motion. That is, the linear imaging unit includes a linear imaging device which is oriented to image across the elements of a data carrying graphical symbol, so that as the linear imaging unit is moved along the height of the symbol, a plurality of imaging events cause a plurality of data sample sets comprising linear image data to be collected. Importantly, if position information is also collected with each data sample set of imaging data collected, it is possible to process the collected data sample sets and select a subset to yield a plurality of preferably evenly spaced imaging positions along the height of the imaged data carrying graphical symbol. As shown in FIG. 1A, processing can be employed to reduced a possibly large plurality of collected data sample sets to yield a subset of data sample sets that are suitably spaced (as clearly depicted in FIG. 1A). It may also be noted that the processing of the image position values will enable the nearly ideal depiction of FIG. 1A to be realized—almost independent of the rate at which the linear imaging unit is swept from a first or start-of-scanning position to a second or end-of-scanning position. Further, a linear imaging unit including a position determining module enables a capturing and collecting of the data sample sets at a sufficiently high rate, such that when processed a plurality of spaced imaging lines (or positions) as depicted in FIG. 1B may be determined. It is contemplated that with a high speed linear imaging unit, it should certainly be possible to provide several data sample sets for each row of the stacked portion 34 of the 2-dimensional data carrying graphical symbol 20a of FIG. 1B.
Accordingly, what is needed is a low-cost linear imaging arrangement that is capable of capturing and collecting a plurality of data sample sets of imaging data taken at discrete positions along the height of an imaged data carrying graphical symbol, while also collecting a unique and or relative position value for each collected data sample set. A processing of collected data sample sets and associated position values may then be employed to select a subset of data sample sets for additional processing to determine at least one or more print quality attributes for the imaged graphical symbol. More specifically, it would be most preferable to provide a means and method wherein a plurality of spaced imaging lines or scans may be captured and collected, with an associated position value also stored with each image line captured. In this way, if an operator is moving or sliding the linear imaging unit at a non-uniform or inconsistent rate, the position information can be employed to select a subset of captured imaging lines, which provides the desired plurality of substantially evenly spaced imaging lines. A number of other characteristics, advantages, and or associated novel features of the present invention, will become clear from the description and figures provided herein. Attention is called to the fact, however, that the drawings are illustrative only. In particular, the embodiments included and described, have been chosen in order to best explain the principles, features, and characteristics of the invention, and its practical application, to thereby enable skilled persons to best utilize the invention and a wide variety of embodiments providable that are based on these principles, features, and characteristics. Accordingly, all equivalent variations possible are contemplated as being part of the invention, limited only by the scope of the appended claims.